Laser therapy is used in many different treatment scenarios, from Acupuncture through to surgery recovery. The therapeutic value of laser light was discovered by accident. Surgeons noticed that surgeries that were performed using laser scalpels healed faster and better than when using traditional metal scalpels. Surgical laser devices required only a simple defocusing of the beam to be used effectively for therapy and thus are an ideal vehicle for experimentation with the therapeutic value of laser light. Due to this simple repurposing of existing technology, modern therapy lasers remain almost identical to their surgical predecessors.
While various treatment modalities uses the same basic laser technology to produce laser light, each has a different requirement for how the light is emitted (leaves the treatment device). Some modalities require tight focus of the beam down to a point (for acupuncture), others require a larger diffused beam (pain management) and certain specialized cases require that the laser light is projected in the shape of the anatomy being treated (for example a long rectangle for treating the entire spine). Laser beam geometries and the limited capabilities of refractive lenses make it difficult to achieve ideal projections patterns or shapes. Lenses simply take the poor geometry of the laser beam and expand or compress it to a different size. Traditionally laser therapy devices use lenses to expand the laser beam, but have limited ability to alter the geometry. An operator compensates for these deficiencies by “painting” the treatment area. Some devices automatically steer the treatment head during use but these are very expensive. Finally, some devices use multiple laser diodes to provide simultaneous treatment over an area. What is needed is a laser therapy device that can disperse the output laser light in a wide variety of geometries in order to accommodate the requirement of different treatment modalities.
Laser therapy is characterized by dose-dependence, meaning that higher doses typically yield improved treatment outcomes. This has resulted in laser therapy devices becoming progressively more powerful over time. While higher power facilitates greater efficacy, it also increases the attendant risks of operating such devices. The high energy levels may cause injury if not properly administered. What is needed is a high-power laser therapy device that automatically regulates the energy output of the laser therapy device during treatment in order to reduce the risk of such injury.
The present invention is directed toward a cordless, high-powered, laser therapy device. Current high power therapy lasers are based upon surgical lasers, due to the maturity of surgical laser technology and the easy repurposing for therapy. However, surgical lasers were developed to be stationary since they were intended to be used on immobile patients. There was no need or desire to make a surgical laser as a handheld or cordless device. Patients are placed under general anesthetic and are brought to the machine's location.
Although surgical and therapy lasers are almost identical in construction, their uses are very different. These different uses give rise to opportunities for an improved design of a laser device for therapy, but also present significant engineering hurdles. Specifically;
(1) Surgical lasers are used to cut tissue to a defined depth. They have a very narrow range of uses. Therapeutic laser devices on the other hand are used for many different conditions including pain, inflammation, wound healing, neuromuscular reeducation and many others.
(2) When a surgical laser has sufficient power to perform an incision, additional power is neither beneficial nor desired. When used for therapy, higher power usually improves treatment (as long as tissue is not overheated). Thus there is a tendency to use higher power laser therapy devices as this improves both treatment outcomes and the time efficiency of treatment.
(3) Surgical lasers require a single narrow beam of light. Therapy lasers require a dispersed beam. A broad dispersed beam is often preferred for therapy because it enhances safety.
(4) Surgical lasers require exact control of power output as this determines the depth of cut. Therapy lasers are concerned more with “dose” or accumulated radiation, so lower power can be used at the expense of longer treatment time.
(5) Surgical lasers are required to heat tissue so hot that it evaporates, whereas therapy lasers must not be allowed to cause discomfort, let alone tissue damage.
(6) Surgical lasers are directed at a very small area with great precision. Therapy lasers are moved around to cover large areas resulting in higher probability of stray radiation.
Laser therapy devices vary principally in output power. The range is a few milliwatts to tens of watts. Like any light source, a laser diode is not 100% efficient. Waste energy is liberated as heat, so thermal management for high-power laser therapy devices is a major issue. Modern laser diodes are roughly 50% efficient. This means that half of the supplied electrical power is converted to light output and the other half is converted to heat. In high power laser therapy devices, this “waste” heat presents two engineering problems. Laser diode efficiency and life degrade at elevated temperatures. Dumping heat into the surrounding air requires a large cooling apparatus. Overheating is the most common cause of laser therapy device failures.
In addition, high power laser therapy devices consume significant electrical power. In order to operate as a cordless device, large batteries are required. This causes such devices to be overly heavy and cumbersome and be seen as impractical.
Therapy lasers have historically been repurposed surgical lasers. Manufacturers have simply applied different heads to diverge the beam (at the end of the fiber that carries the light output) and applied different software to existing surgical devices. Although some of these devices were “portable,” they are portable only in the sense that the entire unit could be moved. There has yet to be a self-contained, handheld laser therapy unit. No manufacturer has yet designed and implemented such a therapy laser device. The most obvious reason is the ease of repurposing existing technology (surgical lasers). In addition, the creation of a portable, high-power, handheld laser therapy device requires a multi-disciplinary approach to overcome engineering hurdles that span high-power optics, miniaturization of electronic, miniaturized of thermal imaging, advanced thermal management, energy management and ergonomics.
The present invention overcomes these limitations. One embodiment of the invention is directed toward a cordless, high-powered, laser therapy device. “High-powered” means any laser therapy device with optical power output of five (5) watts or higher, although the same technology could be employed to benefit lower power devices. The cordless, handheld, embodiment of the laser provides a great advantage in situations where a patient requires treatment in a specific position which would be awkward or impractical to treat with a corded device. Likewise, a cordless, handheld, laser therapy unit would be beneficial for treating animals in the care of a veterinarian.
Because of the limitations in the current state of the art, handheld laser therapy devices are not high powered. Laser diodes typically require around 20% of the maximum input electrical power before they start emitting light. Therefore at low output power levels the conversion rate of electrical power to optical power is very low.
The current invention uses a novel approach for improving efficiency of the laser diodes at lower output power requirements (and therefore minimizing electrical power consumption). The maximum efficiency of the laser diodes is when they are operating at maximum output power. The invention employs two mechanisms for adjusting the total output power of the device while the laser diodes are running at maximum output. Firstly, the invention disables a portion of the array of diodes. Those laser diodes that are switched on are operating at or near their maximum power but since there are fewer, the net laser power emitted from the device is reduced. The second mechanism is to pulse the diodes between off and on very rapidly and to vary the percentage of time that the diode is in the “on” state. This technique of “Pulse Width Modulation” is used to provide a much finer degree of control than selective disabling of parts of the laser diode array.